I personally do not believe ePub is optimized code at all!
From there my complaint, if I would have invented the epub, I would have given it the options it now has, but I would have optimized code to look more like the code in this post:
https://www.mobileread.com/forums/sho...27&postcount=3
and not make any hyperlinks and headers mandatory for coding the page.
If you understand anything about coding an HTML document, I've included 2 html's for you to take a look at.
This is what I call "optimal coding".
One is the smallest chapter I could find in the new testament. I chose that one, because not the text of the bible matters here, but the coding done to create this page.
The other is a bible framework I used from before I had only the Sony PRS-505 reader, which was only able to read LRF files back in the days.
LRF files do not support an internal toc, so I had to create one from scratch in HTML format.
If you look at both pages, it's possible, but very difficult to make the coding overhead any smaller than this (see files below).
I had to compress the file, because this site does not allow uploading of HTML files.